$\textbf{Câu 15:}$
$\text{.............................................................................................................}$
$\textbf{Giả thiết:}$
$\text{a $\bot$ c}$
$\text{b $\bot$ c}$
$\text{$\widehat{F_{1}}$ = $130^o$}$
$\textbf{Kết luận:}$
$\text{CMR: a // b}$
$\text{Tính $\widehat{E_{1}}$, $\widehat{E_{2}}$, $\widehat{E_{3}}$, $\widehat{E_{4}}$}$
$\text{............................................................................................................}$
$\textbf{Giải}$
$\text{a/ Ta có: a $\bot$ c (gt)}$
$\text{b $\bot$ c (gt)}$
$\text{nên a // b (T/c 1 quan hệ từ vuông góc đến song song)}$
$\text{Vậy a // b (đpcm)}$
$\text{b/ a// b (cmt)}$
$\text{Nên $\widehat{F_{1}}$ = $\widehat{E_{4}}$ (slt)}$
$\text{$\widehat{F_{1}}$ = $\widehat{E_{2}}$ (đv)}$
$\text{$\widehat{F_{1}}$ + $\widehat{E_{1}}$ = $180^o$ (tcp)}$
$\text{T/S: $130^o$ + $\widehat{E_{1}}$ = $180^o$}$
$\text{⇒ $\widehat{E_{1}}$ = $180^o$ - $130^o$ = $50^o$}$
$\text{$\widehat{E_{1}}$ = $\widehat{E_{3}}$ = $50^o$ (đđ)}$
$\text{Vậy $\widehat{E_{2}}$ = $\widehat{E_{4}}$ = $130^o$}$
$\text{$\widehat{E_{1}}$ = $\widehat{E_{3}}$ = $50^o$}$
$\textit{HỌC TỐT NHA!}$